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Old 17-01-2014, 19:34   #16
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Re: DSC poling question

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Originally Posted by goboatingnow View Post
Yes message 19 is a holdover from the unimplemted. aIS class B SOTDMA specification. ( as it uses two slots. ) AIS class B can respond to message request 18, 19, 24 all of which provide position reports. 18, 24 are single slot protocols and can be requested from any equipped class A system , because message 19, is a two slot system , only the base station as defined in the ITU/IMO spec can guarantee reception of message 19. ( CSTDMA is a single slot system only )

Again if you turn off the transmitter you cannot respond to the few class B telecommands. In fact to my knowledge some leisure AIS units don't even implement these features.

It's certainly not what you feel it is.

Dave
What I feel has nothing to do with whether these units are transponders or not. If they transmit information when polled from another unit then they are in fact transponders, not transceivers. The op wanted to know if law enforcement could poll his dsc to get his position without his knowledge. I simply stated that he may have been confusing dsc with ais. You have simply confirmed my statement with the proviso that if you have the transmtter turned off they cannot do so. Of course if you have it on you'll be announcing the same infrormation every couple of minutes anyway.
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Old 17-01-2014, 19:39   #17
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Re: DSC poling question

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Originally Posted by Captain Bill View Post
What I feel has nothing to do with whether these units are transponders or not. If they transmit information when polled from another unit then they are in fact transponders, not transceivers. The op wanted to know if law enforcement could poll his dsc to get his position without his knowledge. I simply stated that he may have been confusing dsc with ais. You have simply confirmed my statement with the proviso that if you have the transmtter turned off they cannot do so. Of course if you have it on you'll be announcing the same infrormation every couple of minutes anyway.
A transponder is a device that only responds to commands , ie its transmits a " response". aIs is primarily a transceiver in that its transits data without any command.

Anyone can issue message 18 requests to get the position data , but since such data is already being transmitted on a regular basis , I fail to see what point you are making. aIS does not transmit your information without your knowledge , I mean you switched it on to do just that thing , ie transmit you position !!!!

You make it sound like its " doing it behind your back " , that's tin hat stuff.

Dave
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